# stress vector variable calculation

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 December 11, 2020, 06:59 stress vector variable calculation #1 New Member   Join Date: Dec 2017 Posts: 2 Rep Power: 0 Hello! I want to calculate the shear stress for my 3D flow in a channel in the streamwise direction. To do so I used the code below. I can obtain the shear stress for any given volume by integrating the calculated stress tensor. However, I want to see the distribution of shear stress like any given variable i.e. the stress at each node. A couple of questions: 1) I've calculated tau for each node but i cannot find the variable for the normal vector. Would simply calculating, for example, {taux} x {Y Grid K Unit Normal} be appropriate for txy (t = stress vector)? 2) my fluid quantities are calculated in the cartesian x-direction but in curved channel areas I need them to be streamwise. I can adjust direction using the equation below, but i'm unsure how best to apply it to every node in a region. Currently, my method is A) select region using pick & select tool, B) value blank to just show region, C) calculate variable using the above equation. It feels a bit clunky and i'm unsure of the results (at least until 1 is sorted). Is there a better method? Equation for variable adjustment (t= stress vector): t =ρ(tzx cosθ + txy sin⁡θ) Code for calculating stress tensor: {D} = {dUdX} + {dVdY} + {dWdZ} {T11} = 0.00089 * (2 * {dUdX} - 2/3 * {D}) - {Pressure} {T12} = 0.00089 * ({dVdX} + {dUdY}) {T13} = 0.00089 * ({dWdX} + {dUdZ}) {T22} = 0.00089 * (2 * {dVdY} - 2/3 * {D})-{Pressure} {T23} = 0.00089 * ({dVdZ} + {dWdY}) {T33} = 0.00089 * (2 * {dWdZ} - 2/3 * {D}) - {Pressure} {taux} = {T11} * {X Grid K Unit Normal} + {T12} *{Y Grid K Unit Normal} + {T13} * {Z Grid K Unit Normal} {tauy} = {T12} * {X Grid K Unit Normal} + {T22} *{Y Grid K Unit Normal} + {T23} * {Z Grid K Unit Normal} {tauz} = {T13} * {X Grid K Unit Normal} + {T23} *{Y Grid K Unit Normal} + {T33} * {Z Grid K Unit Normal} Apologies if this has been asked previously - looked through the older posts and couldn't find anything.

 Tags shear stress, tecplot, unit normal